1.Field of the Invention
The present invention relates to a high throughput, single pass direct transfer roll web based color printer utilizing a simplified tandem engine architecture.
2. Description of Related Art
Many designs of color printers and copiers have been proposed. One type of copier utilizes a single engine architecture, requiring the multi-pass transfer of three primary color images onto a copy paper. However, there is a severe drawback to the throughput limitations of single engine color copiers.
For higher productivity, multiple engines in tandem types of architectures have been proposed. One common approach utilizes an intermediate transfer belt to accumulate sequentially all of the primary images, then the composite image is transferred to copy paper in a single pass.
Another approach utilizes a paper escort mechanism to bring the paper in contact with the different color engines for image transfer to take place. Examples of this utilize a chain gripper or a large drum with a mesh screen.
U.S. Pat. No. 4,531,828 to Hoshino discloses a color copier having a tandem engine architecture. The color copier comprises four sets of laser beam printer mechanisms, an insulative screen belt formed of meshes of fibers and driven by a pair of belt driving rollers, a paper supply mechanism and a fixing device. This design utilizes a belt to engage and drive a paper through the copier to provide multicolor images thereon. This design has inherent problems with registration and attempts to remedy the problem by designing lengths between tandem engines of the copier to equal a circumference of a drive roll.
U.S. Pat. No. 5,016,062 to Rapkin discloses a multicolor copier which comprises a primary imaging member (a conductive endless web), four secondary imaging members, a charging station, an exposure station, a development station, transfer stations, and a cleaning station. The secondary imaging stations are in the form of drums and each include a fusing station, a charging station and a toning station.
U.S. Pat. No. 4,994,858 to Lubberts discloses a multicolor copier comprising an endless imaging web supported by a large diameter drum and at least one small diameter roller. First and second electrostatic images are created and toned on a same portion of the web as it is moved by the drum. The toners are of different colors to make a multicolor image. The multicolor image is transferred to a receiving sheet which contacts the endless imaging web near the small diameter roller.
U.S. Pat. No. 5,043,761 to Johnson discloses a multicolor copier which includes a transfer roller for registering single color images. The copier includes an imaging drum and multiple toning stations. A series of electrostatic images are formed on the image drum and toned with different colors. The toners are transferred in registration to a portion of a continuous web receiving sheet by securing a portion of the web to a transfer roller in a first direction to receive an image and in a second direction to return the portion of the web to a position for receiving a second web image in registration. This does not provide for single pass multicolor printer and utilizes an intermediate imaging member and a transfer roller.
U.S. Pat. No. 4,773,270 to Nishikawa et al. discloses a multicolor copier which forms images of a plurality of colors in a superimposed manner on an identical unrolled portion of a recording web. The copier reciprocates an identical portion of the web a plurality of times to an image forming/processing station. This copier has low throughput due to the use of multiple passes to provide a multicolor image.
There are numerous problems associated with known color copiers. Multiple pass color copiers have reduced throughput and additionally require multiple iterations of advancing a transfer material, transferring an image portion corresponding to a particular primary color, and backing the transfer material to the starting location. This requires complex tracking, sensing and control to ensure quality image registration when the images are superimposed. Transient errors due to drives and roller components starting, stopping and accelerating are commonplace and hard to overcome without sophisticated, high- cost hardware to minimize or take account for these errors.
Single pass color copiers having only moderate throughput and usually have complex control and sensing requirements to ensure proper registration. This is due to the large number of interrelated components and many sources for registration and timing errors. This is primarily brought about due to positional errors between print engines, intermediate rollers and the image receiving sheet. Slippage may occur continually or intermittently between these interrelated components, causing registration errors. Additionally, multiple sensors and other hardware must control the relative velocities and accelerations of the components to ensure proper registration.